1. Field of the Invention
The present invention relates to an anti-vibration lens attachment which can be used with, for example, a CCTV (monitoring camera).
2. Description of the Related Art
There two known types of anti-vibration lenses which absorb vibration applied to a photographing lens system and form an image on an image forming surface (image pickup surface) of a camera body; i.e., an integrated anti-vibration lens which includes a correction lens group made integral with the photographing lens system (master lens), the lens being movable in a direction perpendicular to the optical axis direction, and an attachment type in which an anti-vibration lens system including a correction lens group is supported on an attachment which is detachably inserted between the photographing lens system and the camera body. In either type, vibration applied to the camera body is detected so that the correction lens group is moved in a direction perpendicular to the optical axis in accordance with the magnitude and the direction of the vibration to eliminate an image blur on the image forming surface. There are known various types of vibration detection devices and drive mechanisms for anti-vibration lenses.
In attachment type anti-vibration lenses, the anti-vibration lens system is arranged between the photographing lens system (master lens) and the image surface thereof in the camera body. Namely, the anti-vibration lens system is located in front of a position in which the image is formed by the photographing lens system, so that the image forming position is shifted rearward by a displacement corresponding to the thickness of the attachment (distance between mounts which are provided at the front and rear ends of the attachment to connect the same to a photographing lens and a camera body) to thereby form an image on an image forming surface of the camera body.
It is desirable that no substantial change in the focal length of the master lens is caused by the anti-vibration lens attachment (i.e., the magnification is approximately 1). However, if the magnification is approximately equal to 1, it is difficult to obtain a sufficient thickness of the attachment. Consequently, it is difficult to construct an anti-vibration lens system whose number of lens elements are enough to correct aberrations.